Influence of cationic, anionic, and non-ionic surfactants on in-situ growth of polyaniline on alumina ceramic membranes for the effective crude oil-in-water emulsion separation: Experimental and machine learning approaches

To improve the effectiveness of oil-water separation during produced water (PW) treatment, three types of surfactants (anionic, cationic, and non-ionic) were used in this work to alter in-situ growth of polyaniline (Pani) as an active layer onto an alumina (Al₂O₃) substrate. This study utilized sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Pluronic F-127 (p-F127) to modify the Pani surface characteristics during an in-situ emulsion polymerization process over an Al₂O₃ substrate. The most homogeneous and stable active layer growth was observed for the Pani-SDS polymer, which was confirmed by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). The surface morphology, chemical modification, and structural features of the Pani-modified Al₂O₃ membranes were confirmed using various characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) diffractograms. The surface wettability of different Pani-modified Al₂O₃ membranes was also studied, and the results of Pani-SDS@ Al₂O₃ membrane displayed a high contact angle of 154.1° for oil (super-oleophobic) underwater as opposed to 151.7° for Pani-CTAB@Al₂O₃ and 149.7° for Pani-p-F-127@Al₂O₃ membranes. At 2 bar, Pani-SDS@Al₂O₃ membranes' flux with pure water and permeate flux with crude oil-in-water emulsion were 7292.4 L·m⁻²·h⁻¹ and 3068.5 L·m⁻²·h⁻¹, respectively. Pani-SDS@Al₂O₃ membrane oil-water separation efficiency was significantly higher than the bare Al₂O₃ and other PANI decorated membranes fabricated in the current study, reaching up to 98.5 %. The strength of the approach is supported by the machine learning models, particularly the SVM, which have achieved an excellent R² of 0.95 on both permeate flux and separation efficiency. With significant operational and environmental ramifications, this work demonstrates the good potential of Pani-SDS-modified membranes in treating oily wastewater.